Self‐Aggregation‐Controlled Rapid Chemical Bath Deposition of SnO₂ Layers and Stable Dark Depolarization Process for Highly Efficient Planar Perovskite Solar Cells

Abstract

Planar perovskite solar cells (PSCs) incorporating n-type SnO₂ have attracted significant interest because of their excellent photovoltaic performance. However, the film fabrication of SnO₂ is limited by self-aggregation and inhomogeneous growth of the intermediate phase, which produces poor morphology and properties. In this study, a self-controlled SnO₂ layer is fabricated directly on a fluorine-doped tin oxide (FTO) surface through simple and rapid chemical bath deposition. The PSCs based on this hydrolyzed SnO₂ layer exhibit an excellent power conversion efficiency of 20.21 % with negligible hysteresis. Analysis of the electrochemical impedance spectroscopy on the charge transport dynamics indicates that the bias voltage influences both interfacial charge transportation and the ionic double layer under illumination. The hydrolyzed SnO₂ -based PSCs demonstrate a faster ionic charge response time of 2.5 ms in comparison with 100.5 ms for the hydrolyzed TiO₂ -based hysteretic PSCs. The results of quasi-steady-state carrier transportation indicate that a dynamic hysteresis in the J-V curves can be explained by complex ionic-electronic kinetics owing to the slow ionic charge redistribution and hole accumulation caused by electrode polarization, which causes an increase in charge recombination. This study reveals that SnO₂ -based PSCs lead to a stabilized dark depolarization process compared with TiO₂ -based PSCs, which is relevant to the charge transport dynamics in the high-performing planar SnO₂ -based PSCs.